The display devices of certain circuit breakers can indicate the status “operative readiness” or “ok” when all requirements for operating a circuit breaker are fulfilled. These requirements are e.g. that the circuit breaker is switched off, the energy store is loaded, the circuit breaker is fully inserted in a framework, or the tripping unit is ready. If all these requirements are fulfilled, the circuit breaker is ready to operate and can be switched on. If one of the requirements is not fulfilled, the display will indicate a problem by displaying a non-operative-status. The operator does not get an indication, why the circuit breaker is not ready to operate. He has to check the circuit breaker to find the problem.